Abstract

Although most patients with type 1 diabetes (T1D) retain some functional insulin-producing islet β cells at the time of diagnosis, the rate of further β cell loss varies across individuals. It is not clear what drives this differential progression rate. CD8+ T cells have been implicated in the autoimmune destruction of β cells. Here, we addressed whether the phenotype and function of autoreactive CD8+ T cells influence disease progression. We identified islet-specific CD8+ T cells using high-content, single-cell mass cytometry in combination with peptide-loaded MHC tetramer staining. We applied a new analytical method, DISCOV-R, to characterize these rare subsets. Autoreactive T cells were phenotypically heterogeneous, and their phenotype differed by rate of disease progression. Activated islet-specific CD8+ memory T cells were prevalent in subjects with T1D who experienced rapid loss of C-peptide; in contrast, slow disease progression was associated with an exhaustion-like profile, with expression of multiple inhibitory receptors, limited cytokine production, and reduced proliferative capacity. This relationship between properties of autoreactive CD8+ T cells and the rate of T1D disease progression after onset make these phenotypes attractive putative biomarkers of disease trajectory and treatment response and reveal potential targets for therapeutic intervention.

Figure 4

The frequency of islet-specific phenotypes among islet-specific CD8+ T cells was assessed for subjects with 5 or more Tmr+ events. (A) Frequencies in HCs (n = 13) as a function of age based on DISCOV-R results from Figure 2. Statistical significance was determined by Spearman’s correlation. (B) Frequencies in T1D subjects who were not classified as rapid or slow progressors, grouped by disease duration (<5 years, n = 3, solid orange circles; ≥5 years, n = 5, open purple diamonds) on the basis of DISCOV-R results from Figure 1. A 2-way ANOVA with Sidak’s test for multiple comparisons revealed no statistically significant differences between the groups. Data represent the mean ± SD. (C) Frequencies in T1D subjects (n = 4) with samples drawn at 2 time points following disease onset, shown as paired, stacked bar graphs. The time points of the first draw were 3.2, 3.8, 4.8, and 5.5 years after disease onset, respectively.